1. Technical Field
Example embodiments generally relate to a fixing device temperature control method, a fixing device, and an image forming apparatus, and more particularly, to a fixing device temperature control method performed by a fixing device for fixing a toner image on a recording medium, the fixing device, and an image forming apparatus incorporating the fixing device.
2. Background Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having two or more of copying, printing, scanning, facsimile, plotter, and other functions, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of a photoconductor; an optical writer emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a development device supplies toner to the electrostatic latent image formed on the photoconductor to render the electrostatic latent image visible as a toner image; the toner image is directly transferred from the photoconductor onto a recording medium or is indirectly transferred from the photoconductor onto a recording medium via an intermediate transfer belt; finally, a fixing device applies heat and pressure to the recording medium bearing the toner image to fix the toner image on the recording medium, thus forming the image on the recording medium.
Such fixing device may include a fixing rotary body, such as a fixing roller and a fixing belt, and a pressing roller pressed against the fixing rotary body to form a fixing nip therebetween through which a recording medium bearing a toner image is conveyed. As the recording medium passes through the fixing nip, the fixing rotary body heated by a heater and the pressing roller apply heat and pressure to the recording medium to melt and fix the toner image on the recording medium.
The image forming apparatuses incorporating such a fixing device are required to form the toner image on various types of the recording media such as coated and uncoated paper and thin and thick paper. Additionally, the low-speed image forming apparatuses may convey fewer recording media at low speed and may be turned off after printing. Conversely, the high-speed image forming apparatuses may convey more recording media at high speed continuously. Under those conditions, the fixing device incorporated in such image forming apparatuses is required to achieve a desired fixing quality consistently.
To address this requirement, the image forming apparatus may change one or more image forming conditions for forming the toner image according to information about the recording medium input by a user, as disclosed by JP-H08-137341-A.
Alternatively, the fixing device may change a fixing condition for fixing the toner image on the recording medium according to information about the recording medium such as the surface property, the thickness, and the moisture content of the recording medium, as disclosed by JP-2006-195422-A.
At the same time, to save energy, the fixing device may be configured so as to not control the temperature of the pressing roller that does not contact an unfixed toner image. However, if the temperature of the pressing roller is not controlled during a print job, fluctuation in the temperature of the pressing roller may adversely affect fixing quality. For example, since the fixing rotary body is heated sufficiently to achieve the desired fixing quality even if the temperature of the pressing roller is relatively high, the pressing roller may overheat, which in turn overheats the recording medium. Accordingly, without controlling the temperature of the pressing roller, the temperature of the recording medium may fluctuate, varying fixing quality and wasting energy.